Cylinder

http://acm.sdut.edu.cn/sdutoj/problem.php?action=showproblem&problemid=2374

思路：三分枚举。

 #include <cstdio>

 #include <cmath>

 #include <cstring>

 #include <algorithm>

 #define maxn 1000100

 using namespace std;

 const double eps=1e-;

 const double pi=acos(-1.0);

 double w,h;

 double ok(double x,int flag)

 {

     double max1=;

     double k=h;

     double s=w;

     double r=(x>s)?s:x;

     double ss=pi*(r/)*(r/);

     double ll=pi*r;

     double c=k-x;

     double r1=(k-x)>s?s:(k-x);

     if(s>=ll&&flag==)

     {

         double v1=ss*c;

         max1=max(max1,v1);

     }

     if(c>=ll&&flag==)

     {

         double v2=ss*s;

         max1=max(max1,v2);

     }

     double s1=pi*(r1/)*(r1/);

     double l1=pi*r1;

     if(s>=l1&&flag==)

     {

         double v3=s1*x;

         max1=max(v3,max1);

     }

     if(x>=l1&&flag==)

     {

         double v4=s1*s;

         max1=max(max1,v4);

     }

     return max1;

 }

 int main()

 {

     while(scanf("%lf%lf",&w,&h)!=EOF)

     {

         if(w==&&h==) break;

         double l=,r=h;

         double ans=,ans1=;

         while(r-l>eps)

         {

             double mid1=(r+l)/;

             double mid2=(l+mid1)/;

             if(ok(mid1,)>=ok(mid2,))

             {

                 ans=mid1;

                 l=mid2;

             }

             else

                 r=mid1;

         }

         l=,r=w;

         while(r-l>eps)

         {

             double mid1=(r+l)/;

             double mid2=(l+mid1)/;

             if(ok(mid1,)>=ok(mid2,))

             {

                 ans1=mid1;

                 l=mid2;

             }

             else

                 r=mid1;

         }

         printf("%.3lf\n",max(ok(ans,),ok(ans1,)));

     }

     return ;

 }